The method for identifying a rotor resistance of an induction motor at standstill in prior art is mainly implemented by injecting voltage step signals into the induction motor, collecting current signals within a certain period of time during dynamic variation of a phase current at stator side, calculating a rotor time constant according to equations and the variance of the current during this period of time, and then calculating the rotor resistance under the condition that the rotor inductance is known.
The above method is achieved on the premise that the rotor inductance is known and the rotor time constant is kept to be fixed during the collection of the current. However, in actual process, excitation circuit inductances may vary depending on different excitation current, and thus the rotor time constant is not a fixed value during the whole measurements. Meanwhile, there are some assumed conditions during derivative processes of the equations, and thus the rotor time constant obtained by the above method is only a approximation and only can be used for the occasions where the requirements to the precision of the rotor time constant is low.
The method for identifying the rotor resistance of the induction motor at standstill in prior art has the following problems: the calculation process is complex, and there are too many approximations during the derivative processes which lead to poor precision of the identified results.